Supervisors info:
Δάλλα Χριστίνα, Αναπληρώτρια Καθηγήτρια Φαρμακολογίας , Ιατρικής Σχολής, ΕΚΠΑ
Summary:
The term stress is used to describe all the requirements (internal or external), which according to the assessment of the individual, put to the test and / or exceed their available capabilities. It has been shown that stress can affect cognitive functions and change the way a person perceives a situation. It can also contribute to the worsening of symptoms of various diseases, such as schizophrenia, attention deficit hyperactivity disorder, etc. The common feature shared by all the above diseases is the inability of the individual to maintain constant attention. So, it can be assumed that there is a relationship between stress and attention. On the other hand, sustained attention is responsible for controlling many different subtypes of perception. Therefore, disorders caused by stress could lead to various cognitive deficits.
What is particularly interesting is that, while it is well known that stress contributes to the reduction of sustained attention, the neurochemical mechanisms by which this is achieved are unknown. One hypothesis is that corticotropin releasing factor (CRF), whose function has been found to be stress-related, has the ability to alter the action of corticosteroid-dependent circuits in the basal forebrain (BF), which are necessary to maintain attention. By researching how and/or if CRF regulates cholinergic functions we could understand better how stress affects cognitive function. To this end, rats were injected with either artificial cerebrospinal fluid (aCSF) or CRF (30 ng or 100 ng) in BF to evaluate the effect of CFR administration on BF.
The main technique used to evaluate the behavioral results of the experiment was the Sustained Attention Task (SAT). At the end of the experiments, the rats were euthanized, and brain tissues were isolated from the PFC and BN (Nucleus Bacalis of Meynert) region. Quantitative and qualitative determination was then performed on the samples from these regions in order to measure the levels of the various neurotransmitters.
The aim of this study was to develop a method to separate adequately and in rapidly amino acids, which are found under normal conditions in nerve cells, and also act as neurotransmitters. The detection was performed by high pressure liquid chromatography with electrochemical detector (HPLC-ED). The amino acids that were analyzed are glutamic acid (GLU), serine (SER), glycine (GLY), glutamine (GLN), alanine (ALA), taurine (TAU) and γ-aminobutyric acid (GABA).
Due to the fact that CRF was administered to BN, the changes observed at the levels of the various neurotransmitters in this region were more pronounced than the changes that occurred in the PFC. At the same time, in pilot experiments it was observed that the ability to understand the absence of a signal was slightly reduced in the rats that were given CRF. The ability to understand the significance of the absence of a signal was affected by the GABA function. It would therefore be expected that the GABA levels that are present under normal conditions (aCSF) in both BN and PFC to be at equivalent or higher levels than those observed in the rats that received CRF. This hypothesis is consistent with the results that were obtained from the quantitative analysis.
Finally, this new method could be used as a means of confirming various scientific hypotheses and contribute significantly to the validation of an experimental hypothesis, thus making it an extremely important research tool.
Keywords:
HPLC-ED, neurochemical assessment, amino acids, rats
